06615: scud: Scud Racer regression, now just a black screen on launch.

Description

As before, I use the 'scud' set to benchmark. Phil fixed it a few revs. back when it was crashing. Now however it just displays a black screen when attempting to play (fwiw, the bench results are off too if run as 'mame64.exe scud -bench 90').

The UART introduced a high-frequency clock (500KHz), which has caused the scheduling quanta to be greatly reduced. The mftb instruction requires 100 cycles to execute but due to the way it is handled in the PPC DRC, there are never enough cycles in a scheduling period for it to execute and thus advance to the next instruction.

Moving generate_update_cycles() to the end of the instruction sequence of mftb resolves the issue but I'm not familiar enough with PowerPC or MAME's DRC to be confident that this is the correct fix.

No.13984

Phil Bennett

Developer

Jul 17, 2017, 01:12

Yeah, that's not correct.

Perhaps all that is required is to change the allow_exception parameter of the early call to generate_update_cycles() to false to allow the instruction to run regardless of the cycles remaining?

No.14444

Osso

Developer

Nov 19, 2017, 08:30

With today's updates it gets to car and course selection, but then it hangs when it should go to the start line.

No.14939

Robbbert

Developer

Apr 10, 2018, 07:07

Currently it shows the settings, then the message "CANCELLED NETWORK BOARD NOT PRESENT", then it goes back to the settings screen in a loop.

No.15274

Hydreigon

Tester

31 days ago

Go into test and change the link ID to single. Preliminary comm board emulation has been done so there is no "Cancelled" message and instead goes into the usual network check. Other than that, the regression is still the same.